1. Field
One embodiment of the invention relates to a disk drive configured to calculate a head rebound distance and which allows rebound of a head to be suitably adjusted when the head collides against a stopper of a ramp during a head unload operation.
2. Description of the Related Art
In general, if a power supply to a disk drive is interrupted, a head flying above a disk needs to be quickly unloaded onto a retract site called a ramp. For example, Jpn. Pat. Appln. KOKAI Publication No. 2005-116085 (hereinafter referred to as Prior Art Document 1) discloses the use of a retract capacitor charged by a power supply, as a current source (or voltage source) allowing the head to be unloaded when the power supply is interrupted. Prior Art Document 1 discloses that the distance that the unloaded head rebounds toward the disk as a result of collision against the stopper of the ramp varies depending on the ambient temperature of the device.
In the head unload technique described in Prior Art Document 1 (this technique is hereinafter referred to as the first head unload technique), the retract capacitor starts discharging in accordance with the interruption of the power supply to the disk driver. The discharge from the retract capacitor is continued for a duration determined by the detected ambient temperature (detection temperature). Then, a current output by the capacitor is supplied to a voice coil motor for the duration determined by the detection temperature. According to the first head unload technique, the head is unloaded under operation power corresponding to the detection temperature. Thus, the head rebound distance can be inhibited from exceeding a given value.
On the other hand, Jpn. Pat. Appln. KOKAI Publication No. 2005-174511 (hereinafter referred to as Prior Art Document 2) discloses a head unload technique for matching the moving speed of a head with a target speed when the head is unloaded (this technique is hereinafter referred to as a second head unload technique). The second head unload technique utilizes speed feedback control for detecting the head moving speed at a predetermined sampling period and based on the detected moving speed, matching the head moving speed with the target speed.
Prior Art Document 2 also discloses the calculation of the moving distance of the head based on the integration of the head moving speed detected at the predetermined sampling speed. Prior Art Document 2 also discloses determination of whether or not the head unload operation has been completed based on the calculated moving distance.
As described above, Prior Art Document 1 discloses the first head unload technique for inhibiting the head rebound distance from exceeding the given value when the head is unloaded in accordance with the interruption of the power supply. However, Prior Art Document 1 fails to disclose a mechanism for calculating the head rebound distance. On the other hand, Prior Art Document 2 discloses the mechanism for calculating the head moving distance from the head moving speed and based on the calculated moving distance, determining whether or not the head unload operation has been completed. However, Prior Art Document 2 fails to disclose a mechanism for calculating the head rebound distance.
Thus, to measure the head rebound distance according to the conventional art, it is necessary to open a housing for the disk drive in the room temperature environment and record the operation of disk drive. Furthermore, according to the conventional art, the number of disk drives that can be measured and a measurement environment are limited. In a high-temperature environment, the sliding resistance between the head and the ramp is low, resulting in an increased rebound distance. Thus, according to the conventional art, measuring the head rebound distance in the high-temperature environment is difficult.